As shown circuit 555 is at the core of the flash circuit, when their normal work, the light emitting diode and VD2 will VDl alternating flashing circuit principle summarized as
follows: The base circuit NE555 and Rl, R2, Cl composed of low-frequency oscillator. After the start-up circuit, time base circuit 555 is 3 feet high and low potential of changing, when 3 feet high when, VDl loss of power does not emit light, VD2 powered light; when 3 feet is low, VDl powered luminous, VD2 loss of power It does not emit light. Therefore, the two light-emitting diodes will flash alternately light. When specific production, the two light-emitting diodes use red, green or yellow, some of the difference may be more visible.